An undercover agent is a person who works in secret to investigate and gather information. The term can be broken down into several crossword solutions: SPY (3 letters), PLANT (5 letters), NARC (4 letters), MOLE (4 letters), OPERATIVE (9 letters), and BULLETPROOFVEST (15 letters). A SPY is someone who collects information without being detected, a PLANT is someone who is sent to infiltrate an organization, a narc is a law enforcement officer who specializes in drug-related crimes, a MOLE is someone who is placed within an organization to report back to another, an OPERATIVE is a person who carries out a mission or task, and a bulletproof vest is a protective garment worn by agents to protect them from gunfire.